CN110918494A - Method for testing metal impurity precipitation voltage in battery and application thereof - Google Patents
Method for testing metal impurity precipitation voltage in battery and application thereof Download PDFInfo
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- CN110918494A CN110918494A CN201911157357.XA CN201911157357A CN110918494A CN 110918494 A CN110918494 A CN 110918494A CN 201911157357 A CN201911157357 A CN 201911157357A CN 110918494 A CN110918494 A CN 110918494A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
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Abstract
The invention discloses a method for testing the precipitation voltage of metal impurities in a battery and application thereof, wherein the testing method comprises the following steps: preparing an experimental group positive plate and a blank group positive plate, wherein the coating surface of the experimental group positive plate is doped with metal impurities; manufacturing a full cell by using the positive plate of the experimental group and the positive plate of the blank group; connecting the positive electrode and the negative electrode of the full battery with formation equipment, connecting the positive electrode and the negative electrode of the full battery and a reference electrode with three voltage channels, namely a positive electrode/a negative electrode, a positive electrode/a reference electrode and a negative electrode/the reference electrode of a multi-channel voltage recorder, charging the full battery, and testing potential curves of the three different voltage channels of the full battery by using the multi-channel voltage recorder; comparing the potential curve diagram of the full cell, the voltage of the positive electrode and the negative electrode of the full cell of the experimental group, which is increased or decreased compared with the full cell of the blank group, is the initial precipitation voltage of the metal impurities. The test method can quickly monitor the precipitation potential and precipitation speed of metal impurities with different compositions under different multiplying powers.
Description
Technical Field
The invention belongs to the field of lithium batteries, and particularly relates to a method for testing the precipitation voltage of metal impurities in a battery and application thereof.
Background
The production process of the lithium ion battery anode material is more, and each link in the manufacturing process has the risk of introducing metal foreign matters. When metal impurities such as iron (Fe), copper (Cu), zinc (Zn), nickel (Ni) and the like exist in the anode material, after the voltage of the battery formation stage reaches the oxidation-reduction potential of the metal elements, the metal elements are firstly oxidized at the anode and then reduced at the cathode, and when metal simple substances at the cathode are accumulated to a certain degree, the metal simple substances pierce through a diaphragm, so that the self-discharge of the battery is caused. However, if the voltage in the formation stage does not reach the oxidation-reduction potential of the metal elements, complete precipitation of metal impurities cannot be guaranteed, and the self-discharge battery leakage risk can occur. In the later cycle of these self-discharge batteries, metal foreign matters are gradually precipitated along with the progress of charge and discharge, which affects the safety and cycle life of the batteries. In order to gradually dissolve and precipitate the metal impurities in the formation stage, it is necessary to study the precipitation potential and precipitation rate of each metal. However, in the current lithium battery manufacturing enterprises, the precipitation potential of the metal impurities is not deeply studied and the formation process of the battery is designed by combining the precipitation potential of the metal impurities, and the screening of the self-discharge battery cells is only carried out by high-temperature aging and normal-temperature aging. The disadvantages of this original process are: 1. the production period is long and the cost is high; 2. the metal impurities can not be effectively separated out in the formation stage, and the risk of the subsequent production process and the leakage rate of the self-discharge battery are increased. Therefore, how to quickly screen the selected discharge cells/batteries remains to be investigated.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. To this end, an object of the present invention is to propose a method of testing the evolution voltage of metal impurities in a battery and its application. The testing method can utilize a three-electrode system to quickly monitor the precipitation potential and precipitation speed of metal impurities with different compositions under different multiplying powers, so that a reasonable formation process can be formulated or adjusted, and pressurization and high-temperature aging are further combined, so that the screening efficiency of the self-discharge battery caused by the metal impurities is remarkably improved.
According to a first aspect of the invention, a method of testing the evolution voltage of metal impurities in a battery is presented. According to an embodiment of the invention, the method comprises:
(1) preparing an experimental group positive plate and a blank group positive plate, wherein the two groups of positive plates are different in that: doping metal impurities on the coating surface of the experimental group positive plate in the positive coating process;
(2) manufacturing an experimental group full cell by using the experimental group positive plate, and manufacturing a blank group full cell by using the blank group positive plate, wherein the full cell comprises a positive electrode, a negative electrode and a reference electrode;
(3) connecting the positive electrode and the negative electrode of the blank group full cell with formation equipment, simultaneously connecting the positive electrode, the negative electrode and the reference electrode of the blank group full cell with a positive electrode/negative electrode voltage channel, a positive electrode/reference electrode voltage channel and a negative electrode/reference electrode voltage channel of a multi-channel voltage recorder respectively, charging the blank group full cell by using the formation equipment, and testing potential curves of three different voltage channels of the blank group full cell by using the multi-channel voltage recorder;
(4) repeating the operation of step (3) on the full cell of the experimental group under the same conditions so as to obtain potential graphs of three different voltage channels of the full cell of the experimental group;
(5) and comparing potential curve graphs of the experimental group full cell and the blank group full cell, wherein the voltage of the positive electrode and the negative electrode of the experimental group full cell, which is increased or decreased compared with that of the blank group full cell, is the initial precipitation voltage of the metal impurities.
The method for testing the precipitation voltage of the metal impurities in the battery provided by the embodiment of the invention at least has the following advantages: 1. the scheme is simple and feasible, the precipitation potentials of the metal impurities with different compositions can be researched, and the precipitation speeds of the metal impurities with specific compositions under different multiplying powers can be researched by further setting charging flows with different multiplying powers; 2. when the method is used for screening the self-discharge battery caused by the metal impurities, a reasonable formation flow can be formulated based on the precipitation potential of the metal impurities and the precipitation speed under different multiplying powers, or the formation flow is adjusted according to different production conditions, so that the rapid precipitation of the metal impurities is ensured, the production period can be shortened, the production cost is reduced, the screening efficiency of the self-discharge battery caused by the metal impurities can be obviously improved, and the risk of the subsequent production process and the omission rate of the self-discharge battery are reduced.
In addition, the method for testing the precipitation voltage of the metal impurities in the battery according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, in step (1), the metal impurity is a single metal or a mixture of metals.
In some embodiments of the present invention, the metal impurity is at least one selected from the group consisting of iron, copper, zinc, nickel, and tin.
In some embodiments of the present invention, the metal impurities have a particle size of 80 to 120 μm.
In some embodiments of the present invention, in step (1), the metal impurities are spread on the coated surface of the positive electrode sheet of the experimental group, or mixed with the positive electrode material and coated on the surface of the current collector.
In some embodiments of the present invention, the mass ratio of the metal impurities to the cathode material is (0.1-1): 100.
in some embodiments of the invention, in step (2), the reference electrode is a metallic lithium sheet, and the reference electrode tab is a metallic nickel strip.
In some embodiments of the present invention, in the steps (3) to (4), when the blank group/experimental group full battery is charged, the first charging rate is 0.01 to 0.1C.
In some embodiments of the present invention, in steps (3) to (4), the blank/experimental group full cells are charged at different charge rates, so as to compare the precipitation rates of the metal impurities at the different charge rates.
According to a second aspect of the invention, the invention proposes the use of the above-described method for testing the evolution voltage of metal impurities in a battery in a self-discharge battery screening caused by metal impurities. The inventor finds that a reasonable formation process can be formulated according to the precipitation potential of the metal impurities and the precipitation speed under different multiplying powers, or the formation process can be adjusted according to different production conditions, so that the rapid precipitation of the metal impurities is ensured, the production period can be shortened, the production cost is reduced, the screening efficiency of the self-discharge battery caused by the metal impurities can be obviously improved, and the risk of the subsequent production process and the rate of the leakage of the self-discharge battery are reduced.
According to a third aspect of the present invention, a method for rapidly precipitating metal impurities in a battery is provided. According to an embodiment of the invention, the method comprises:
(i) obtaining initial precipitation voltage and/or precipitation speed of the metal impurities in the battery based on the method for testing the precipitation voltage of the metal impurities in the battery;
(ii) and determining the formation condition of the battery and carrying out formation and aging on the battery based on the initial precipitation voltage and/or the precipitation speed so as to rapidly precipitate the metal impurities in the battery.
According to the method for rapidly precipitating the metal impurities in the battery, a reasonable formation process can be formulated based on the precipitation potential of the metal impurities and the precipitation speed under different multiplying powers, or the formation process can be adjusted according to different production conditions, so that the rapid precipitation of the metal impurities is ensured, and further, the precipitation rate of the metal impurities can be further improved by combining a pressurizing and high-temperature aging mode. Therefore, the method can shorten the production period, reduce the production cost, remarkably improve the screening efficiency of the self-discharge battery caused by metal impurities, and reduce the risk of the subsequent production process and the rate of the self-discharge battery missing judgment.
In some embodiments of the invention, in step (ii): and pre-forming the battery, and then carrying out pressurization and high-temperature aging on the formed battery.
In some embodiments of the present invention, the pressurizing pressure of the pressurizing high-temperature aging is 0.4 to 0.6Kg/cm2The temperature is 40-60 ℃ and the time is 3-5 days.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a flow chart of a method of testing the extraction voltage of metal impurities in a battery according to one embodiment of the invention.
Fig. 2 is a connection mode of the full cell, the formation equipment and the multi-channel voltage recorder in the method for testing the precipitation voltage of the metal impurities in the cell according to one embodiment of the invention.
Fig. 3 is a schematic view of electrodes of a full cell according to one embodiment of the present invention.
Fig. 4 is a tab schematic of a reference electrode according to one embodiment of the present invention.
Fig. 5 is a potential graph of a blank set of full cells according to one embodiment of the present invention.
Fig. 6 is a graph of positive/reference electrode potentials for different experimental parameters for test and blank full cells, according to one embodiment of the present invention.
Reference numerals: 10-formation equipment; 20-multichannel voltage recorder; 30-full cell.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The inventor unexpectedly finds that when the metal impurities in the battery begin to be separated out, the potentials of the positive electrode and the negative electrode of the battery are increased or decreased compared with the potential of the battery without the metal impurities, and the voltage between the corresponding positive electrode and the corresponding negative electrode when the metal impurities begin to be dissolved and separated out under specific conditions can be effectively monitored and judged by designing a three-electrode system. Therefore, in the method for testing the precipitation voltage of the metal impurities in the battery according to the embodiment of the invention, the positive electrode and the negative electrode of the three electrodes of the full battery are connected to form equipment, and the potentials of the positive electrode and the negative electrode are continuously monitored by using a multi-channel voltage recorder, so that the potential curve diagrams of the battery with the metal impurities doped in the positive electrode plate and the battery without the metal impurities doped in the positive electrode plate are tested and compared, and the initial precipitation voltage of the metal impurities in the battery is obtained.
To this end, according to a first aspect of the invention, the invention proposes a method of testing the evolution voltage of metal impurities in a battery. According to an embodiment of the invention, as shown in fig. 1, the method comprises: (1) preparing an experimental group positive plate and a blank group positive plate, wherein the two groups of positive plates are different in that: doping metal impurities on the coating surface of the anode plate of the experimental group in the anode coating process; (2) manufacturing an experimental group full cell by using the experimental group positive plate, and manufacturing a blank group full cell by using the blank group positive plate, wherein the full cell comprises a positive electrode, a negative electrode and a reference electrode; (3) as shown in fig. 2, the positive electrode and the negative electrode of the full cell 30 of the blank set are connected to the formation device 10, and the positive electrode, the negative electrode and the reference electrode of the full cell of the blank set are respectively connected to the positive electrode/negative electrode voltage channel, the positive electrode/reference electrode voltage channel and the negative electrode/reference electrode voltage channel of the multi-channel voltage recorder 20, the full cell of the blank set is charged by the formation device, and the potential curve diagram of three different voltage channels of the full cell of the blank set is tested by the multi-channel voltage recorder; (4) repeating the operation of step (3) on the experimental group full cell 30 under the same conditions so as to obtain potential graphs of three different voltage channels of the experimental group full cell; (5) and comparing potential curve diagrams of the experimental group full cell and the blank group full cell, wherein the voltage of the positive electrode and the negative electrode of the experimental group full cell, which is increased or decreased compared with the blank group full cell, is the initial precipitation voltage of the metal impurities.
The method of testing the precipitation voltage of metal impurities in the battery according to the above-described embodiment of the present invention is described in detail mainly from two parts.
(I) preparing a positive plate and a three-electrode full cell
According to the embodiment of the invention, the experimental group positive plate and the blank group positive plate are prepared, and the two groups of positive plates are different in that: doping metal impurities on the coating surface of the anode plate of the experimental group in the anode coating process; the method comprises the steps of manufacturing an experiment group full cell by using an experiment group positive plate, manufacturing a blank group full cell by using a blank group positive plate, wherein the full cell comprises a positive electrode, a negative electrode and a reference electrode.
According to an embodiment of the present invention, the metal impurities may be a single metal or a mixture of metals, so that the deposition voltage of each single metal or the deposition voltage of a mixture of metals under a specific charging process can be tested according to different requirements. The inventors found that the extraction voltage may vary when a plurality of metal impurities are mixed as compared with a single metal impurity, and therefore, in actual production, when a plurality of metal impurities are present in the positive electrode material, it is preferable to mix a plurality of metal impurities to prepare the positive electrode sheet and the full cell, whereby the accuracy of the test result can be further improved.
According to still another embodiment of the present invention, the kind of the metal impurities in the present invention is not particularly limited, and those skilled in the art can select the metal impurities according to the kind of the metal impurities which may be mixed in the battery in actual production. For example, the metal impurities may be at least one selected from the group consisting of iron, copper, zinc, nickel, and tin.
According to another embodiment of the present invention, the metal impurities may have a particle size of 80 to 120 μm, for example, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm or 120 μm, and the inventors have found that the deposition voltage of the metal impurities is not affected by the particle size of the metal impurities, but if the particle size of the metal impurities is too small, the deposition rate of the metal impurities is high, the force for piercing the battery diaphragm is small, the amplitude of the positive and negative electrode potentials of the battery rising or falling compared with that of a blank group is influenced, the testing sensitivity is low, and if the particle size of the metal impurities is too large, although the strength of piercing the diaphragm by the metal impurities can be improved, the separation speed of the metal impurities is slow, and the sensitivity of the test can be influenced. According to another embodiment of the present invention, the metal impurities may be applied to the coated surface of the positive electrode sheet of the experimental group, or may be mixed with the positive electrode material, the conductive material and the binder and then applied to the surface of the current collector, so that the metal impurities may be uniformly dispersed on the positive electrode sheet.
According to another embodiment of the invention, the mass ratio of the metal impurities to the positive electrode material can be (0.1-1): 100, the inventor finds that when the doping amount of the metal impurities is low, the positive and negative electrode potentials of the battery are increased or decreased by a small amount compared with a blank group when the metal impurities are separated out, and the test sensitivity is low, and when the mass ratio of the metal impurities to the positive electrode material is too large, short circuit is easily caused in the test process, so that the accuracy of the test result is seriously influenced.
According to another embodiment of the present invention, the full cell may be a lithium battery, the reference electrode of the full cell may be a metallic lithium sheet, and the reference electrode tab may be a metallic nickel strip, so that the stability of the test result may be further improved. Specifically, as shown in fig. 3, a metal lithium sheet as a reference electrode is inserted between the electric core layers, the electric core is coated with an aluminum-plastic film, the positive and negative electrode side edges and the reference electrode side edge are heat-sealed, liquid is injected, vacuum is pumped, and then heat-sealing is performed to obtain a three-electrode full battery; as shown in fig. 4, the reference electrode tab may be composed of an adhesive tape and a metallic nickel strip penetrating through the adhesive tape, a metallic lithium sheet is folded to wrap one end of the reference electrode tab, the lithium sheet is rolled, and the lithium sheet and the reference electrode tab are tightly attached and then wrapped by a diaphragm. The sizes of the lithium metal sheet and the nickel metal strip in the invention are not particularly limited, and those skilled in the art can select a lithium metal sheet and a nickel metal strip with appropriate sizes according to specific battery models, for example, the size of the lithium metal sheet can be 8-10 mm long, 5-8 mm wide and 0.5-1 mm thick, and the size of the nickel metal strip can be 3-5 mm wide and 0.2-0.4 mm thick.
(II) testing and comparing potential curve graphs of experimental group full batteries and blank group full batteries
According to the embodiment of the present invention, as shown in fig. 2, the positive electrode and the negative electrode of the full cell blank set 30 are connected to the formation device 10, and simultaneously the positive electrode, the negative electrode and the reference electrode of the full cell blank set are respectively connected to the positive electrode/negative electrode voltage channel, the positive electrode/reference electrode voltage channel and the negative electrode/reference electrode voltage channel of the multi-channel voltage recorder 20, the full cell blank set is charged by using the formation device, and the potential curve diagrams of three different voltage channels of the full cell blank set are tested by using the multi-channel voltage recorder; repeating the operation on the full cells of the experimental group under the same condition so as to obtain potential graphs of three different voltage channels of the full cells of the experimental group; and comparing potential curve diagrams of the experimental group full cell and the blank group full cell, wherein the voltage of the positive electrode and the negative electrode of the experimental group full cell, which is increased or decreased compared with the blank group full cell, is the initial precipitation voltage of the metal impurities. Therefore, the precipitation potentials of the metal impurities with different compositions can be researched, and the precipitation speeds of the metal impurities with specific compositions under different multiplying powers can be researched by further setting the charging flows with different multiplying powers.
According to one embodiment of the invention, when the blank group/experiment group full battery is charged, the first charging rate can be 0.01-0.1C, and the battery is charged firstly by adopting small current, so that the formed SEI film has better effect.
According to another embodiment of the present invention, the blank group/experimental group full cells may be charged at different charging rates, for example, the blank group/experimental group full cells may be charged at charging rates of 0.05C, 0.1C, 0.2C, etc., so that the precipitation speeds of the metal impurities at different charging rates may be compared according to the variation rates of the positive and negative electrode potential diagrams, and further, a more reasonable battery formation process may be determined by integrating the precipitation voltages and precipitation speeds of the different metal impurities and the influence of each metal on the cell performance.
According to yet another embodiment of the present invention, each blank group and each experimental group may be tested multiple times and/or repeated with multiple identical samples, respectively, in order to further improve the accuracy of the test results.
In summary, the method for testing the metal impurity precipitation voltage in the battery according to the above embodiment of the present invention has at least the following advantages: 1. the scheme is simple and feasible, the precipitation potentials of the metal impurities with different compositions can be researched, and the precipitation speeds of the metal impurities with specific compositions under different multiplying powers can be researched by further setting charging flows with different multiplying powers; 2. when the method is used for screening the self-discharge battery caused by the metal impurities, a reasonable formation flow can be formulated based on the precipitation potential of the metal impurities and the precipitation speed under different multiplying powers, or the formation flow is adjusted according to different production conditions, so that the rapid precipitation of the metal impurities is ensured, the production period can be shortened, the production cost is reduced, the screening efficiency of the self-discharge battery caused by the metal impurities can be obviously improved, and the risk of the subsequent production process and the omission rate of the self-discharge battery are reduced.
According to a second aspect of the invention, the invention proposes the use of the above-described method for testing the evolution voltage of metal impurities in a battery in a self-discharge battery screening caused by metal impurities. The inventor finds that a reasonable formation process can be formulated according to the precipitation potential and the precipitation speed of the metal impurities under different multiplying powers, or the formation process can be adjusted according to different production conditions, so that the metal impurities can be rapidly precipitated, and further, the precipitation rate of the metal impurities can be further improved by combining a pressurizing high-temperature aging mode. Therefore, the production period can be shortened, the production cost can be reduced, the screening efficiency of the self-discharge battery caused by metal impurities can be obviously improved, and the risk of the subsequent production process and the rate of the self-discharge battery missing judgment can be reduced.
According to a third aspect of the present invention, a method for rapidly precipitating metal impurities in a battery is provided. According to an embodiment of the invention, the method comprises: (i) obtaining initial precipitation voltage and/or precipitation speed of the metal impurities in the battery based on the method for testing the precipitation voltage of the metal impurities in the battery; (ii) and determining formation conditions of the battery and carrying out formation and aging on the battery based on the initial precipitation voltage and/or precipitation speed and the influence of the metal impurities on the battery performance so as to rapidly precipitate the metal impurities in the battery. By adopting the method, the production period of the battery can be shortened, the production cost can be reduced, the screening efficiency of the self-discharge battery caused by metal impurities can be obviously improved, and the risk of the subsequent production process and the rate of the leakage of the self-discharge battery can be reduced.
According to an embodiment of the present invention, the battery can be previously commercializedThe inventor finds that when the metal impurities reach the oxidation-reduction potential, the metal impurities are firstly oxidized at the positive electrode and then reduced at the negative electrode, and are attached to the surface of the negative electrode in a simple substance form, and the deposited metal can be accelerated to pierce through the diaphragm by the pressurization mode, so that the self-discharge is promoted, the screening efficiency is improved, and the high-temperature aging can accelerate the generation of side reactions and can promote the stability of an electrochemical system. Therefore, the separation speed of the metal impurities can be further improved by adopting a pressurizing high-temperature aging mode after formation, so that the screening efficiency and the screening speed of the self-discharge battery caused by the metal impurities can be further improved. Specifically, the pressurizing pressure for pressurizing the high-temperature aging can be 0.4-0.6 Kg/cm2The temperature can be 40-60 ℃, and the time can be 3-5 days.
In summary, the method for rapidly precipitating metal impurities in a battery according to the above embodiment of the present invention may formulate a reasonable formation process based on the precipitation potential and precipitation speed of the metal impurities under different rates, or adjust the formation process according to different production conditions, so as to ensure rapid precipitation of the metal impurities, and further, may further improve the precipitation rate of the metal impurities by combining with a pressurized high-temperature aging method. Therefore, the method can shorten the production period, reduce the production cost, remarkably improve the screening efficiency of the self-discharge battery caused by metal impurities, and reduce the risk of the subsequent production process and the rate of the self-discharge battery missing judgment. It should be noted that the features and effects described above for the method for testing the precipitation voltage of the metal impurities in the battery are also applicable to the method for rapidly precipitating the metal impurities in the battery, and are not repeated here.
The scheme of the invention will be explained with reference to the examples. It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Method for testing metal impurity precipitation voltage in battery
General procedure
(1) Preparing an experimental group positive plate and a blank group positive plate, wherein the two groups of positive plates are different in that: metal impurities are scattered on the coating surface of the anode plate of the experimental group in the anode coating process;
(2) the method comprises the following steps of manufacturing an experimental group full cell by utilizing an experimental group positive plate, manufacturing a blank group full cell by utilizing a blank group positive plate, wherein the full cell comprises a positive electrode, a negative electrode and a reference electrode, the reference electrode is a metal lithium plate, and a reference electrode tab is a metal nickel strip;
(3) connecting the positive electrode and the negative electrode of the blank group full cell with automatic formation equipment, simultaneously connecting the positive electrode, the negative electrode and the reference electrode of the blank group full cell with a positive electrode/negative electrode voltage channel, a positive electrode/reference electrode voltage channel and a negative electrode/reference electrode voltage channel of a multi-channel voltage recorder respectively, charging the blank group full cell by using the formation equipment, and testing potential curve graphs of three different voltage channels of the blank group full cell by using the multi-channel voltage recorder;
(4) repeating the operation of the step (3) on the full cell of the experimental group under the same condition so as to obtain potential graphs of three different voltage channels of the full cell of the experimental group;
(5) and comparing potential curve diagrams of the experimental group full cell and the blank group full cell, wherein the voltage of the positive electrode and the negative electrode of the experimental group full cell, which is increased or decreased compared with the blank group full cell, is the initial precipitation voltage of the metal impurities.
The automatic formation equipment is high-temperature pressure formation equipment of a soft package battery with constant wing energy, and the multichannel voltage recorder is a multichannel voltage acquisition recorder with the model of BY.9-YBJL-310.
Examples 1 to 4
The parameter conditions for the blank and examples 1-4 (i.e., four different experimental groups) are shown in table 1, and the test results are shown in table 2 and fig. 5 and 6.
TABLE 1 blank set and parametric conditions for examples 1-4
TABLE 2 initial precipitation voltage and precipitation rate at different charge rates of metal impurities in examples 1 to 4
Results and conclusions:
fig. 5 is a graph of the potential of undoped metal three electrodes (blank) at 0.05C charge rate. As can be seen from the graph, the positive/reference electrode potential gradually increased with the charging process, roughly from 3100mV to 4400mV and leveled off; the negative/reference electrode potential was then gradually decreased from 3100mV to about 200 mV; the cell voltage (positive/negative) is the difference between the two, gradually increasing from 0 to 4200mV and tending to plateau.
FIG. 6 is a comparison of the results of the examples, based on the parameters in Table 1, comparing the trend of the positive electrode/reference electrode potential. As can be seen from the figure, the positive electrode potential of the doped metal battery has a obvious voltage platform at about 3850mV, the platform is the dissolution of the metal impurities of iron and copper, and the end of the platform is the end of the dissolution process. Comparing and analyzing the example 1 and the example 2 by combining the table 2, the charging rate is increased, the positive electrode potential is increased more rapidly, and the dissolving speed of the metal impurities is increased (example 2:11min, example 3:6 min); comparative analysis of example 1 and example 3, the metal impurities increased and the metal dissolution rate decreased for the same charge rate (11 min for example 2 and 13min for example 4).
In summary, it is shown that: the dissolving potential of the metal impurities has no obvious relation with the metal doping amount and the charging rate; the dissolving speed of the metal impurities becomes slow along with the increase of the metal doping amount; the metal impurity dissolution rate increases and the battery charge rate becomes faster.
(II) method for rapidly precipitating metal impurities in battery
The general method comprises the following steps: the cells containing iron and copper as metallic impurities were subjected to formation and pressurized high-temperature aging under the conditions of formation and pressurized high-temperature aging shown in table 3, based on the initial precipitation voltage and precipitation rate of the metallic impurities in the cells obtained in example 2.
Examples 5 to 7
The parameter conditions are shown in Table 3.
TABLE 3 parameter conditions for examples 5 to 7
Results and conclusions:
the cells were subjected to formation and high temperature aging according to the process parameters in examples 5-7. The self-discharge screening effect is as follows: the miss rate of example 5 was 0.05%; the miss rate of example 6 was 0.08%; the rate of missing judgments in example 7 was 0.12%. The data show that the self-discharge failure rate can be effectively controlled within 0.1% by aging at high temperature for more than or equal to 4 days, and the outflow of the self-discharge cell is reduced.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A method of testing the evolution voltage of metal impurities in a battery, comprising:
(1) preparing an experimental group positive plate and a blank group positive plate, wherein the two groups of positive plates are different in that: doping metal impurities on the coating surface of the experimental group positive plate in the positive coating process;
(2) manufacturing an experimental group full cell by using the experimental group positive plate, and manufacturing a blank group full cell by using the blank group positive plate, wherein the full cell comprises a positive electrode, a negative electrode and a reference electrode;
(3) connecting the positive electrode and the negative electrode of the blank group full cell with formation equipment, simultaneously connecting the positive electrode, the negative electrode and the reference electrode of the blank group full cell with a positive electrode/negative electrode voltage channel, a positive electrode/reference electrode voltage channel and a negative electrode/reference electrode voltage channel of a multi-channel voltage recorder respectively, charging the blank group full cell by using the formation equipment, and testing potential curves of three different voltage channels of the blank group full cell by using the multi-channel voltage recorder;
(4) repeating the operation of step (3) on the full cell of the experimental group under the same conditions so as to obtain potential graphs of three different voltage channels of the full cell of the experimental group;
(5) and comparing potential curve graphs of the experimental group full cell and the blank group full cell, wherein the voltage of the positive electrode and the negative electrode of the experimental group full cell, which is increased or decreased compared with that of the blank group full cell, is the initial precipitation voltage of the metal impurities.
2. The method according to claim 1, wherein in step (1), the metal impurities are a single metal or a mixture of metals,
optionally, the metal impurities are at least one selected from the group consisting of iron, copper, zinc, nickel and tin,
optionally, the particle size of the metal impurities is 80-120 μm.
3. The method according to claim 1 or 2, wherein in the step (1), the metal impurities are spread on the coated surface of the positive electrode sheet of the experimental group, or mixed with the positive electrode material and coated on the surface of the current collector,
optionally, the mass ratio of the metal impurities to the cathode material is (0.1-1): 100.
4. the method of claim 3, wherein in step (2), the reference electrode is a metallic lithium sheet and the reference electrode tab is a metallic nickel strip.
5. The method according to claim 1 or 4, wherein in the steps (3) to (4), when the blank group/experimental group full-cell is charged, the first charge rate is 0.01-0.1C.
6. The method according to claim 5, wherein in steps (3) to (4), the blank/test set full cells are charged at different charge rates so as to compare the precipitation rates of the metallic impurities at the different charge rates.
7. Use of the method of any one of claims 1 to 6 in self-discharge cell screening for metallic impurities.
8. A method for rapidly precipitating metal impurities in a battery, comprising:
(i) obtaining an initial precipitation voltage and/or precipitation rate of metal impurities in a battery based on the method of any one of claims 1-6;
(ii) and determining the formation condition of the battery and carrying out formation and aging on the battery based on the initial precipitation voltage and/or the precipitation speed so as to rapidly precipitate the metal impurities in the battery.
9. The method of claim 8, wherein step (ii) further comprises: and pre-forming the battery, and then carrying out pressurization and high-temperature aging on the formed battery.
10. The method according to claim 9, wherein the pressure of the pressure-high temperature aging is 0.4 to 0.6Kg/cm2The temperature is 40-60 ℃ and the time is 3-5 days.
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